Document start-notebook.sh and start-singleuser.sh

docs/using/selecting.md

@@ -60,6 +60,13 @@ It contains:
 - A `start-singleuser.py` script useful for launching containers in JupyterHub
 - Options for a self-signed HTTPS certificate
 
+```{warning}
+`jupyter/base-notebook` also contains `start-notebook.sh` and `start-singleuser.sh` files to maintain backwards
+compatibility. External config that explicitly refers to those files should instead update to refer to
+`start-notebook.py` and `start-singleuser.py` instead. The shim `.sh` files will be removed at some future
+date.
+```
+
 ### jupyter/minimal-notebook
 
 [Source on GitHub](https://github.com/jupyter/docker-stacks/tree/main/images/minimal-notebook) |